The toric axis marker generally relates to ophthalmology and more specifically to marking the cornea at one or more meridians. The invention relates to placing markings precisely upon a cornea before a surgeon incises the cornea during procedures such as astigmatic keratotomy, limbral relaxing incisions, radial keratotomy, other corneal incisions, other corneal procedures, or a lens replacement.
Developed over the millennia, people have eyes to see. An eye has various tissues that receive and focus light upon a retina that converts the light into electrical signals transmitted to a person's brain for interpretation. In the vicinity of a person, light encounters a cornea as the first part of the eye. The cornea, generally transparent, admits light further into the eye. The cornea has its own constituent parts where the endothelium is the extremely thin, innermost layer of the cornea. Inwardly from the cornea, an eye has its lens of flexible tissue.
Various fine muscles attach to the lens and stretch the lens to adjust its focus as desired by the person seeing an object at a certain distance. The soft lens seeks to modify the focal power of the lens within an eye. The eye lens, inwardly from the cornea, provides the focusing for images. The eye lens comes from concentric protein layers that move well during the youth of a person but then gradually thicken and lose pliability over the years. Reaching the age of forty years, many people then encounter difficulty in focusing because of this eye lens thickening, or presbyopia. Then later in a person's life, the lens may become opaque, creating a condition known as a cataract.
To correct myopia and to some extent presbyopia, surgeons developed the technique of radial keratotomy, also known as RK. The RK technique involves incising the cornea with a radial pattern of incisions. The incisions penetrate the corneal stroma to a predetermined depth. A surgeon uses a diamond bladed knife to make the narrow, deep incisions. The incisions alter the curvature of the cornea and improve the patient's vision.
In other situations, a surgeon makes incisions in the cornea to create a more spherical shape. This treatment of a condition called astigmatism may employ incisions that are tangential or circular to the center of the cornea.
Over a lifetime, the lens hardens, the lens muscles weaken, glaucoma strikes, a cataract grows, and a host of other maladies may affect the lens. Early on, a person's lens would just lose function and focal power. A person would compensate for that with glasses or prescription eye drops as needed. In time, a clouding of the lens can result in blindness. Recently decades have brought advances in both materials and surgical techniques. Surgeons may now replace a lens in a living eye.
In recent years, various physicians and lens manufacturers have attempted to duplicate the ability of a human eye lens to focus at both near and far distances and to remove an existing lens and to install a new lens without blinding a patient.
With RK, astigmatism incisions, and lens replacement, a surgeon incises the eye. The small thickness of the cornea, delicate nature of the eye, and importance of vision to a patient, the surgeon must make precise incisions accurately located. The surgeons utilize various tools often with assisted magnification to make such incisions.